As the only piano virtuoso to become prime minister of Poland, Ignacy Jan Paderewski (1860-1941) may be more trivia answer than major figure for even the most ardent fan of the Romantic era. Those who are familiar with his music probably know the "Polonia" Symphony or his two piano-and-orchestra showpieces, "Polish Fantasy" and the Piano Concerto. A dramatic figure who wore his hair in a great shaggy mane, Paderewski, at left, was a star attraction on the international circuit, celebrated for his fervent interpretations of Chopin as well as his own works. His opera, "Manru," was performed at the Metropolitan Opera in 1902. On this solo piano recording, Jonathan Plowright performs the excitingly bombastic Piano Sonata, Op. 21, and two sets of variations. All three works are variable and erratic, but there's plenty of melodic freshness, structural inventiveness and striking individuality to savor. The sonata is an ambitious three-movement work that runs close to 35 minutes. It begins with a portentous basso-profundo figure, quickly offset by a winsome lyrical line, both of which are thoroughly explored. The composer has a tendency to dwell almost obsessively on certain phrases, repeating and reworking them as if they were fixed immovably in his mind. The Andante has a more modern cast, with Scriabin-like chords in the early going and a plush theme worthy of Rachmaninoff later on. The closing Allegro comes off with a bright, angular intensity. Both sets of variations contain delightful inventions, cheap effects and a handsome fugue at the end. The music is by turns lyrical, tender, propulsive and bizarre (a fussy patter of tone clusters, swooping glissandi). Plowright, who has made lesser-known composers a specialty (his recordings include discs devoted to Zygmunt Stojowski, Walter Rummel and Constant Lambert), performs with conviction and panache. He gives Paderewski his due, revealing the seriousness of purpose, the lighthearted charm and a penchant for self-indulgence.